It can be very difficult to pin down a specific food that you are having problems with. There are many common problem foods, and most people will have an intolerance to several foods. The common offenders are cow's milk, wheat, corn, eggs, soy, sugar, corn syrup, chocolate, rye, barley and peanuts. There are many more, but each person is very unique in their intolerances of food. Then of course, there are all the chemicals that are now added to most of the foods we eat. So get set to do some homework.
Since you are having symptoms all the time, and you feel this is a due to food intolerances, and not something like IBS (irritable bowel syndrome), then trying an "elimination diet", or hypoallergenic diet might help you identify what the offenders are.
I have to note here---IBS can be caused or aggravated by food intolerances.
There are many ways to do this, the most drastic of which is to fast, then slowly re-introduce foods. I would not advise this. The sensible way to do this is to eliminate all foods that are suspect. Since you have been keeping a food diary, you can tell what you eat every day. Do not eat these foods for at least 7 days, and up to 4 weeks. Then eat one. Give it a few days. See what happens. Keeping a diary of all this can be very helpful. If you develop symptoms, stop eating it. If you don't, try a second food.
Here is a simple elimination diet:
Eliminate all of the following foods from your diet:
All dairy products including milk, yogurt, ice cream, cheese.
All foods containing Gluten: wheat products, anything made with flour, barley, oat and rye grains
Eggs, and products containing eggs
Corn, and products containing corn
All processed foods (anything that is prepackaged, bottled, in a jar, not a single food item, and not made by you.)
After at least 7 days (you need to be free of symptoms), reintroduce one food group at a time and monitor the response. Give each food group about 5 to 7 days before adding another.
If you don't have a reaction you can continue to eat this food, then reintroduce another.
If you do have a reaction, stop eating this food, wait until you have no symptoms, then reintroduce the next food group.
If you are faithfully eating an elimination diet, and you are still having symptoms before you start reintroducing foods, you will need to decide which foods to eliminate. An example may be brocolli. You should be able to see which foods are likely offenders from your food diary. It will be simpler to see a pattern once you have eliminated the above foods.